Oxidative desulfurization of hydrocarbons

ABSTRACT

A process that includes:
         mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent in a film-shear reactor under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition;   separating a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition;   oxidizing with ozone the at least one organic sulfur-containing compound in the first phase to produce at least one oxidized organic sulfur-containing compound; and   separating the at least one oxidized organic sulfur-containing compound from the extraction solvent.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/624,893, which was filed on Apr. 16, 2012, and is incorporated herein by reference in its entirety.

ACKNOWLEDGMENT OF GOVERNMENT SUPPORT

This invention was made with government support under contract number W011NF0720083 awarded by the U.S. Department of Defense. The government has certain rights in the invention.

BACKGROUND

Fuels with ultra-low sulfur levels are becoming increasingly important because fuel cells require near-zero sulfur levels and because combusting sulfur-containing fuels has negative health and environmental effects. Current hydro-desulfurization (HDS) technologies convert the sulfur contaminants to H₂S and require high temperatures and pressures for sulfur removal. A further decrease in sulfur levels requires increasingly harsh conditions due to recalcitrant sulfur compounds that are very difficult to remove. A complementary alternative to HDS is oxidative desulfurization (ODS), in which thiophene contaminants are oxidized through their corresponding sulfoxides to sulfones. The resulting sulfones are no longer soluble in the fuel phase and are therefore more easily removed. ODS is also appealing because the sulfur contaminants that are most resistant to HDS are the most reactive under ODS conditions. However, oxidative desulfurization employs an aqueous oxidant (typically hydrogen peroxide with catalytic acid) that must react with the sulfur contaminant in the fuel phase. As a result, hours of stirring at elevated temperatures are required

SUMMARY

One embodiment disclosed herein relates to a process comprising:

mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent in a film-shear reactor under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition;

separating a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition;

oxidizing with ozone the at least one organic sulfur-containing compound in the first phase to produce at least one oxidized organic sulfur-containing compound; and

separating the at least one oxidized organic sulfur-containing compound from the extraction solvent.

Another embodiment disclosed herein relates to a system comprising:

a film-shear reactor configured for mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition;

a first separation module for receiving the product from the film-shear reactor and configured to separate the product into a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition;

an oxidation reactor for receiving the first phase and configured for oxidizing the at least one organic sulfur-containing compound; and

a second separation module for receiving the mixture of extraction solvent and at least one oxidized organic sulfur-containing compound from the oxidation reactor and configured to separate the extraction solvent from the at least one oxidized organic sulfur-containing compound.

The foregoing will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a process flow diagram of one embodiment of the presently disclosed process.

FIG. 2 is a diagram of a film-shear reactor.

DETAILED DESCRIPTION

Disclosed herein are processes and systems for oxidative desulfurization of hydrocarbon (HC) compositions. The hydrocarbon compositions include at least one organic sulfur-containing compound, which typically is present as a contaminant. One example of a hydrocarbon composition is a hydrocarbon fuel. The organic sulfur-containing compound(s) is efficiently and quickly removed from the hydrocarbon compositions. The processes and systems include a film-shear reactor that efficiently mixes the hydrocarbon composition with an organic solvent (e.g., a lactone) that can extract the organic sulfur-containing compound(s) from the hydrocarbon fuel. The organic sulfur-containing compound(s) are subsequently oxidized with an oxidant (e.g., ozone), which enables their separation from the organic solvent. The organic solvent can then be re-used in the processes and systems.

One embodiment of a process is shown in FIG. 1. A HC feed stream that includes at least one organic sulfur-containing compound (e.g., contaminated HC fuel) is introduced into a film-shear reactor. Illustrative HC fuels include heavy cycle oil, diesel, gasoline, kerosene or fuel oil (e.g., bunker fuel). Illustrative organic sulfur-containing compounds include heterocyclic sulfur-containing compounds such as thiophene, benzothiophene, dibenzothiophene, tribenzothiophene, alkylated derivatives of thiophene such as 4-methyl dibenzothiophene, 4,6-dimethyl-dibenzothiophene, 2-methylbenzothiophene, 5-methylbenzothiophene, 2,3,7-trimethylbenzothiophene, 2,3-dimethylbenzothiophene, and combinations thereof. In certain embodiments, the flow rate of the HC feed may range from 0.5 to 1000 mL/min, more particularly 0.5 to 10 mL/min.

Also introduced into the film-shear reactor is an extraction solvent such as a lactone, 1-methyl-2-pyrrolidinone, ethyl heptanoate, or a combination thereof. Illustrative lactone solvents include butyrolactone or valerolactone such as γ-butyrolactone (GBL), γ-valerolactone (GVL) or δ-valerolactone (DBL). The extraction solvent may be from a fresh feed supply (not shown in FIG. 1) or from a recycle stream as described in detail below. The HC feed and the extraction solvent may be mixed prior to entry into the film-shear reactor, or they may be separately introduced via separate inlets into the film-shear reactor.

An example of a film-shear reactor is illustrated in FIG. 2. The reactor features a rotor plate that can be adjusted to within hundreds of microns from a stator plate. This close proximity, combined with rapid rotation of the rotor, subjects the HC and the extraction solvent between the two plates to high shear rates. The design of the reaction zone causes the non-miscible HC and extraction solvent streams to encounter each other under conditions of high shear. Contact of the fluids within this narrow gap results in intense mixing and intimate contact of the two phases. A heat exchanger allows control of the temperature in the reaction zone. Furthermore, unlike the specially designed facilities that are required to accommodate the high temperatures and pressures required for HDS, the small size of the film-shear reactor (10 in. high) in one embodiment makes this technology ideal for portable applications.

The amount of extraction solvent flowing through the film-shear reactor relative to the amount of HC flowing through the film-shear reactor may vary. For example, the flow ratio of extraction solvent to HC may range from 10:1 to 1:10, more particularly 5:1. The gap between the rotor plate and the stator plate may range from 50 to 2000 μm, more particularly 250 to 1500 μm or 150 to 250 μm. The rotor spinning speed may range from 500 to 10,000 rpm, more particularly 1700 to 4000 rpm or 1000 to 2000 rpm. The film-shear reactor temperature may range from 0 to 100° C., more particularly from 45 to 80° C., and most particularly 70 to 80° C.

A heterogeneous mixture of the HC and the extraction solvent forms in the film-shear reactor wherein the organic sulfur-containing compounds are extracted from HC phase into the extraction solvent phase. The mixture product from the film-shear reactor is introduced into a first separation module. An example of a first separation module is a settler as shown in FIG. 1. The mixture product forms a biphasic composition wherein the desulfurized HC phase is the top layer and the extraction solvent/organic sulfur-containing compound phase is the bottom layer. The respective layers may be separated by decanting and/or centrifuging. The desulfurized HC may be removed from the system as a final product and/or a portion of the desulfurized HC may be recycled back to the HC feed stream for reintroduction into the film-shear reactor. The separated extraction solvent/organic sulfur-containing compound phase may be introduced into an oxidation module.

In certain embodiments at least one high molecular weight hydrophilic polymer may be included in the mixing of the hydrocarbon composition and the extraction solvent and/or in the separating of the first phase from the second phase. For example, the high molecular weight hydrophilic polymer may be introduced into the film-shear reactor with the hydrocarbon composition or with the extraction solvent. In a further example, the high molecular weight hydrophilic polymer may be introduced into the first separation module. In certain embodiments, the high molecular weight hydrophilic polymer may have a molecular weight of at least 3000 g/mol, more particularly at least 4000 g/mol, and most particularly at least 10000 g/mol. Illustrative high molecular weight hydrophilic polymers include polyalkylene glycols such as polypropylene glycol and polyethylene glycol.

In the oxidation module the organic sulfur-containing compound(s) are oxidized into the respective sulfone species. In the embodiment shown in FIG. 1 the organic sulfur-containing compound(s) are oxidized by reaction with ozone. The ozone may supplied by an ozone generator (not shown in FIG. 1) in which ozone is generated from an air feed. The concentration of ozone in the feed may be 20 to 50 ppm, more particularly 45 to 50 ppm.

The product from the oxidation module then is introduced into a second separation module. The sulfone species are separated from the extraction solvent in the second separation module, for example, via distillation of the lactone. The extraction solvent may be recycled back to the film-shear reactor.

In certain embodiments the hydrocarbon phase (e.g., the decontaminated HC fuel) separated from extraction solvent/sulfur-containing compound extract phase contains no sulfur that is detectable by gas chromatography. In other embodiments, the separated hydrocarbon phase contains ≦100 ppm by weight sulfur, more particularly ≦10 ppm by weight sulfur. In certain embodiments, the processes and systems described herein may be employed to produce bunker fuel having sulfur content of ≦1000 ppm by weight sulfur.

In certain embodiments the system is portable. For example, the system could be mounted or loaded onto a vehicle (e.g., a truck) so that it could be easily moved from one location to another location. In other examples, the system is sufficiently small so that it can be carried by one or two individuals from one location to another location.

EXAMPLES Extraction with the Film-Shear Reactor

The two input tubes of the KinetiChem Inc. Synthetron™ film-shear reactor were attached to solutions of 0.5% dibenzothiophene (DBT) in decane (used as a model for jet fuel) and to γ-butyrolactone (GBL) (used to extract the DBT from the decane fuel). Each solution was pumped through the reactor at speeds between 0.5 to 2.5 mL/min. The reactor can use gap sizes between 250 and 1500 microns while spinning at speeds between 1600 and 6000 rpm (4 to 16V) and 10° C. to 80° C. Best extraction of the DBT into the GBL was observed during high shear (low gap size and high rotor speed) and high temperature conditions with a 5:1 flow ratio of GBL to decane. The outflow of the film-shear reactor was collected and allowed to settle into a biphasic solution with the decane layer above the GBL layer. Samples of both layers were taken and tested to determine the level of DBT via ¹HNMR or gas chromatography (GC).

TABLE 1 Average Gap Flow Flow Temper- Thiophene Size Speed Rate GBL Rate Fuel ature Extraction (μm) (rpm) (mL/min) (mL/min) (° C.) Run 1 98% 1500 1700 2.5 0.5 10 Run 2 92% 875 4000 1.5 1.5 45 Run 3 92% 875 4000 1.5 1.5 45 Run 4 78% 250 1700 0.5 2.5 10 Run 5 82% 875 4000 1.5 1.5 45 Run 6 89% 250 7000 2.5 2.5 10 Run 7 89% 250 1700 0.5 0.5 10 Run 8 97% 1500 7000 2.5 0.5 80 Run 9 82% 1500 7000 2.5 2.5 80 Run 10 96% 250 7000 2.5 0.5 10 Run 11 84% 1500 1700 0.5 0.5 80 Run 12 55% 250 7000 0.5 2.5 80 Run 13 52% 1500 1700 0.5 2.5 80 Run 14 82% 25 1700 2.5 2.5 80 Run 15 85% 150 1700 2.5 2.5 10 Run 16 96% 250 1700 2.5 0.5 80 Run 17 86% 250 7000 0.5 0.5 80 Run 18 84% 875 4000 1.5 1.5 45 Run 19 85% 1500 7000 0.5 0.5 10 Run 20 61% 1500 7000 0.5 2.5 10

GBL Remediation

The outflow of the extraction was collected and the clean decane was separated by taking off the top layer of the biphasic solution collected from the film-shear reactor. The GBL (the bottom layer) was then treated with ozone at a rate of up to 100 mg/hr. The ozone was generated in an Ozotech Poseidon JR Ozone Generator with dry air and was pumped into the GBL using a needle to the bottom of the reaction vessel. The reaction vessel was fitted with a rubber septum and an outflow through a bubbler. Samples of solution were taken at 45-minute intervals for 360 minutes and a sample was taken after the reaction had proceeded overnight. Samples were analyzed using GC and a standard solution of phenanthrene in GBL was used to standardize the GC traces. After total remediation of the DBT into the respective sulfone species, the GBL can be distilled and recycled through the process.

TABLE 2 Temperature Percent Percent Time Percent Run (° C.) GBL hydrocarbon (min) Desulfurized 1 40 50% 50% 0 2% 1 40 50% 50% 135 84% 1 40 50% 50% 840 91% 2 80 50% 50% 0 16% 2 80 50% 50% 120 92% 2 80 50% 50% 300 97% 3 80 50% 50% 0 10% 3 80 50% 50% 135 88% 3 80 50% 50% 1260 96% 4 80 50% 50% 0 17% 4 80 50% 50% 135 83% 4 80 50% 50% 360 88% 5 80 100% 0% 0 0% 5 80 100% 0% 135 38% 5 80 100% 0% 360 97% 6 80 100% 0% 0 100% 6 80 100% 0% 4230 0% 7 80 100% 0% 0 0% 7 80 100% 0% 135 100% 7 80 100% 0% 180 100% All samples above were initially 500 ppm dibenzothiophene (DBT).

Several illustrative embodiments are described in the following numbered paragraphs:

1. A process comprising:

mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent in a film-shear reactor under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition;

separating a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition;

oxidizing with ozone the at least one organic sulfur-containing compound in the first phase to produce at least one oxidized organic sulfur-containing compound; and

separating the at least one oxidized organic sulfur-containing compound from the extraction solvent.

2. The process of paragraph 1, further comprising recycling the separated lactone back to the mixing step.

3. The process of paragraph 1 or 2, further comprising recycling the separated hydrocarbon composition back to the mixing step.

4. The process of any one of paragraphs 1 to 3, wherein separating the first phase from the second phase comprises decanting or centrifuging.

5. The process of any one of paragraphs 1 to 4, wherein oxidizing the least one organic sulfur-containing compound in the first phase comprises mixing ozone with the first phase.

6. The process of any one of paragraphs 1 to 5, wherein the organic sulfur-containing compound is thiophene, and the thiophene is oxidized to sulfone.

7. The process of any one of paragraphs 1 to 6, wherein separating the at least one oxidized organic sulfur-containing compound from the lactone comprises distilling the lactone.

8. The process of any one of paragraphs 1 to 7, wherein the extraction solvent comprises a lactone.

9. The process of paragraph 8, wherein the lactone comprises γ-butyrolactone.

10. The process of any one of paragraphs 1 to 9, wherein the hydrocarbon comprises a hydrocarbon fuel that is contaminated with the least one organic sulfur-containing compound.

11. The process of any one of paragraphs 1 to 10, further comprising generating ozone from air.

12. A system comprising:

a film-shear reactor configured for mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition;

a first separation module for receiving the product from the film-shear reactor and configured to separate the product into a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition;

an oxidation reactor for receiving the first phase and configured for oxidizing the at least one organic sulfur-containing compound; and

a second separation module for receiving the mixture of extraction solvent and at least one oxidized organic sulfur-containing compound from the oxidation reactor and configured to separate the extraction solvent from the at least one oxidized organic sulfur-containing compound.

13. The system of paragraph 12, further comprising an ozone generator for feeding ozone into the oxidation reactor.

14. The system of paragraph 12 or 13, wherein the first separation module comprises a settler.

15. The system of any one of paragraphs 12 to 14, wherein the second separation module comprises a distillation element.

16. The system of any one of paragraphs 12 to 15, further comprising means for recycling lactone from the second separation module to the film-shear reactor.

17. The system of any one of paragraphs 12 to 16, wherein the system is portable.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. 

What is claimed is:
 1. A process comprising: mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent in a film-shear reactor under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition; separating a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition; oxidizing with ozone the at least one organic sulfur-containing compound in the first phase to produce at least one oxidized organic sulfur-containing compound; and separating the at least one oxidized organic sulfur-containing compound from the extraction solvent.
 2. The process of claim 1, further comprising recycling the separated lactone back to the mixing step.
 3. The process of claim 1, further comprising recycling the separated hydrocarbon composition back to the mixing step.
 4. The process of claim 1, wherein separating the first phase from the second phase comprises decanting or centrifuging.
 5. The process of claim 1, wherein oxidizing the least one organic sulfur-containing compound in the first phase comprises mixing ozone with the first phase.
 6. The process of claim 1, wherein the organic sulfur-containing compound is thiophene, and the thiophene is oxidized to sulfone.
 7. The process of claim 1, wherein separating the at least one oxidized organic sulfur-containing compound from the extraction solvent comprises distilling the extraction solvent.
 8. The process of claim 1, wherein the extraction solvent comprises a lactone.
 9. The process claim 8, wherein the lactone comprises γ-butyrolactone.
 10. The process of claim 1, wherein the hydrocarbon composition comprises a hydrocarbon fuel that is contaminated with the least one organic sulfur-containing compound.
 11. The process of claim 1, further comprising generating ozone from air.
 12. The process of claim 1, wherein the hydrocarbon composition comprises a bunker fuel.
 13. The process of claim 1, further comprising including a high molecular weight hydrophilic polymer in the mixing of the hydrocarbon composition and the extraction solvent and/or in the separating of the first phase from the second phase.
 14. A system comprising: a film-shear reactor configured for mixing a hydrocarbon composition that includes at least one organic sulfur-containing compound with an extraction solvent under conditions wherein the extraction solvent extracts the at least one organic sulfur-containing compound from the hydrocarbon composition; a first separation module for receiving the product from the film-shear reactor and configured to separate the product into a first phase comprising the at least one organic sulfur-containing compound and the extraction solvent from a second phase comprising the hydrocarbon composition; an oxidation reactor for receiving the first phase and configured for oxidizing the at least one organic sulfur-containing compound; and a second separation module for receiving the mixture of extraction solvent and at least one oxidized organic sulfur-containing compound from the oxidation reactor and configured to separate the extraction solvent from the at least one oxidized organic sulfur-containing compound.
 15. The system of claim 14, further comprising an ozone generator for feeding ozone into the oxidation reactor.
 16. The system of claim 14, wherein the first separation module comprises a settler.
 17. The system of any one of claim 14, wherein the second separation module comprises a distillation element.
 18. The system of any one of claim 14, further comprising means for recycling lactone from the second separation module to the film-shear reactor.
 19. The system of any one of claim 14, wherein the system is portable. 